This invention relates to the preparation of cyanate esters. In one aspect, the invention relates to a high-temperature method for preparation of cyanate esters.
Cyanate esters are thermosettable materials of interest in electronics applications because of their ease of processability, low dielectric constants and high glass transition temperatures. One drawback of cyanate esters, however, is that their preparation, which involves the base-catalyzed reaction of a cyanogen halide and a phenolic resin, requires such low temperatures, generally in the range of about -10.degree. to 10.degree. C., as to require refrigeration of the reaction mixture. At higher reaction temperatures, the cyanogen halide appears to react with the basic catalyst, competing with the desired reaction of cyanogen halide with the phenolate salt and lowering the yield of cyanate ester product. It would be desirable, for practical as well as economic reasons, to prepare cyanate esters in good yields at a higher temperature.
It is therefore an object of the invention to provide a relatively high-temperature process for the preparation of cyanate esters.